Membrane proteins, which are present in cell membranes, play an important role in immune reactions and material transports/releases to inside and outside of the cells. Therefore, for the development of the method of therapy and drug discovery in the next generation, it is an important subject to clarify each functions and characteristics of various kinds of membrane proteins.
Typical conventional art for fabricating planar lipid membranes used for analyzing membrane proteins such as an ion channel is a planar membrane method, i.e., brush coating method or LB method (Langmuir-Blodgett method). In both of the methods, a lipid bilayer is formed in a tiny aperture of several hundred microns in size pierced on a Teflon (a trademark) sheet in a chamber filled with buffer solution. In the method of the former, lipid solution is coated on the tiny aperture with a brush. On the other hand, in the method of the latter, the planar lipid membrane is formed by gradually rising solution surface in the chamber on both sides of a Teflon (a trademark) sheet, using such effect that a lipid monolayer is formed on the liquid surface.
FIG. 1 is a schematic view of a conventional LB method of forming a planar lipid bilayer membrane.
In this figure, 101 is a Teflon (a trademark) sheet, 102 is a tiny aperture pierced on the Teflon (a trademark) sheet 101, 103 is the solution on the surface of which a lipid monolayer 104 is formed, and 105 is a buffer solution, and a lipid bilayer membrane 106 is formed by gradually rising the surface of the solution 103 in the chamber on both sides of the Teflon (trademark) sheet 101.
The following are examples of the other methods which have been proposed to the present for forming a lipid bilayer membrane:    (1) A method of forming a lipid bilayer membrane by extending amphipathic molecules at the interface of a liquid trilayer system and removing an intermediate liquid layer (See patent document 1 below).    (2) A method wherein after a surface of one side of a substrate having small through-holes is made in contact with the surface of a first aqueous solution, the solution containing molecules for forming a lipid bilayer membrane is added onto the first aqueous solution in the tiny aperture, and then the second aqueous solution is provided onto the other surface of the substrate (See patent document 2 below).    [Patent document 1] Japanese Patent Application Publication No. 03-118832.    [Patent document 2] Japanese Patent Application Publication No. 05-261277.    [Non-patent document 1] “Ion Channel Reconstitution”, C. Miller Ed., Plenum Press (1986).    [Non-patent document 2] H. Suzuki, K. Tabata, Y. Kato-Yamada, H. Noji, and S. Takeuchi, μ TAS, 2, 246 (2004).    [Non-patent document 3] H. Suzuki, et al., 3rd Int. IEEE-EMBS Special Topic Conf. on Microtechnologies in Medicine and Biology, Hawaii, May 2005.    [Non-patent document 4] T. Ide, Y. Takeuchi, and T. Yanagida, Single molecules, 3, 33 (2002).